5. Creating a Map

In this section, the process of creating a playable Doom level
is explained in detail. The working of the game can be understood
easily once this entire process is described.

Doom levels are built using a software called an Editor. A
number of Level editors are available for free download from the
internet. The editor that I have used here is called DoomCAD.

The DoomCAD Editor is simple to use and has an easy interface.

Fig. 1

Vertices are placed in the map (fig. 2).

Fig. 2

Fig. 3

By joining the vertices with linedefs, a sector is created
(fig. 3). This sector that I have just created consists of four
linedefs. Since the player will be standing inside, he can only
see the sides of these facing him. So all these linedefs are
one-sided.

Each sidedef can have it's own texture, and so I choose
textures for the four sidedefs. I have chosen the GSTONE1 texture
(fig. 4) for all - this will make the walls look as if they are
made of green stone.

Fig. 4

Now I choose properties for the sector. It's brightness is
chosen as 190 (values can be 0-255), and it's floor and ceiling
heights are chosen. The flat to be painted on the floor and
ceiling is also chosen. For example, I have chosen FLAT5_7 (fig.
5) to be displayed on the floor, and this looks like a rocky
floor.

Fig. 5

I then place a player start position in the
corner of the map (fig. 6).

Fig. 6

Then I save the level, and play it in Doom
(fig. 7).

Fig. 7

The engine takes care of using the level information I have
given, and generating this room. Here, I can move around using
the controls in the game and the engine will automatically redraw
the environment so that it looks realistic. I can also shoot with
my weapon, and the engine will take care of playing the sound
effects.

Notice the textures I have chosen - the green stone on the
walls, rocky floor.

This is the way a map in Doom is created. Here a very
simplistic map was shown. An actual playable level must contain
an exit - that is, a special linedef with a property that it can
be activated by the player by pressing a button, which will take
him to the next level.

What we have now defined, is our own WAD file which contains
just enough information for one level. So in this file we will
have 11 lumps, as shown below (fig. 8).

Fig. 8

Our WAD does not contain any other information. The actual
DOOM.WAD file is a huge file containing 2,306 lumps!

An example for a complete level, is as shown below. This is
obviously a lot more complicated than the small sector that was
just shown. This is a completely playable level that contains a
large number of (nearly 70) interconnected sectors.